Method of and apparatus for casting dental aluminium plates.



Patented Sept. I9, |899.

2 Sheets-Sheet l v ,if 0

w. STREETMAN. METHOD DF AND APPARATUS FOR-CASTING DENTAL ALUMINIUMyPLATES.

(Application led Dac. 22, 189.8.) (N0 Model.)

/l/L'nesse:

No. 633,222. yPatented sept. I9, |899.

w. STREETMAN.. f

METHOD 0F AND APPARATUS FOR CASTING DENTAL ALUMINIUM PLATES.

(Applicationled Dec. 22, 1898.)

(No Model.)

2 Sheets-Sheet 2,

UNITED STATES TVILLARD STREETMAN,

PATENT FFIon..

OF CLEBURNE, TEXAS.

METHOD F ND APPARATUS FOR CASTING DNTAL ALUMINIUM PLATES;

SPECIFICATION forming pere of Lettere Patent No. 633,222, datedseptember Ie, ieee.-

Application filed December 22,1898. Serial No. 692.979. (No model.)

T0 @ZZ whom/ it may concern;

Be it known that I, WVILLARD STREETMAN,

v of Cleburne, in the county of Johnson and State of Texas, haveinvented va new and Improved Method of and Apparat-us for Casting DentalAluminium Plates, of which the following is a full, clear, and exactdescription.

The object of my invention is to provide a method of casting aluminiumdental plates that Will provide a perfect product and a plate ofsuperior quality with au expenditure of less time and labor than ispossible under the usual methods, at the same time securing a better titin the mouth.

Another object of the improved method is to provide a means forovercoming all difficulties now present in the casting of plates ofaluminium or its alloy and to so simplify such method or process that itcan be generally employed.

A further object of the invention is to provide an apparatus that willbe simple, durable, and economic and that Will insure the casting ofaperfect plate of pure aluminiumnamely, a plate Without alloy-andwherein the method and apparatus will embody all the advantages ofprevious methods and devices Without their defects.

The invention consists in the novel construction and combination of theseveral parts, as will be hereinafter fully set forth, and pointed outin the claims.

Reference is to be had to the accompanying drawings, forming a part ofthis specification, in which similar characters of reference indicatecorresponding parts in all the figures.

- Figure l is a perspective view of a model `to be employed. Fig. 2 is alongitudinal section through one member of a iiask, showing a model heldin the investment thereof and the upper face of the model provided witha Wax covering. Fig. 3 is a view similar to Fig. 2, in which a secondWaX covering is located above that which is on the model, the tWo Waxcoverings being provided with an intervening gauze and the upper Waxcovering with a stem extendingupwardly therefrom. Fig. 4 is alongitudinal vertical section through thev complete flask, showing theinvestments in both. Fig. 5 is a plan vievvofl the member of the flaskshown in Fig. 3. Fig. 6' is a longitudinal vertical section of the flaskcompleted, as shown in Fig. 4, and set up prior to pouring, illustratingin dotted lines the margins ofthe body-gates to be provided for thefiasks and formed in the investment-s thereof. Fig. 7 is a view similarto Fig. 6, showing the body-gates in the investment of one of themembers of the iiask, the Wax material employed in the formation of themold having been melted out. Fig. 8 is a view similar to Fig. 7,illustrating the metal as having been poured into the mold and the plateas formed. Fig. f) is a perspectiveview of the cast plate and theattached metal removed from the flask after pouring. Fig. l0 is a sideelevation of the complete flask set up for pouring, a portion of one ofthe members being broken away to show the inner face of the member inwhich the model is set. Fig. 1l is an edge view of the iiask set up; andl2 is a perspective view of the finished cast plate, parts being insection, illustrating the application of the teeth to lthe plate.

The difficulties to be overcome in casting aluminium and that prevent itbeing cast in the ordinary Way are, first, it is so light that it willnot force the gas and air out of the mold, and consequently the castpieces are rendered more or less porous; second, the metal when meltedlacks fluidity and will not run sharp; third, shrinkage is extreme anddestroys theintegrity of the plate, and,fourth, contraction isalsovextreme and destroys the tit of the plate. I seek by my methods toovercome all these difficulties Without alloying the metal, althoughalloys maybe cast, as by previous methods.

In carrying out the process an impression is taken in the usual Way, anda plaster model is taken therefrom. From the modela matrix is formed insections, if there are undercuts. A second model, of any material thatwill endure heat, is formed in the matrix. A baseplate of requiredthickness is made upon this model, and teeth are set up or are omittedif other attachments are to be used. Invest in the usual Way in the samematerial as the model or any other material, if desired. The model isthen placed in a flask, the heel of the model being as far as possiblefrom the neck of the flask. The flask is so constructed as toprovideconsiderable space between the IOO heel of the model and the neckof the flask in order that the metal, being light, shall spread andshall distribute itself almost simultaneously and evenly to the entiremold. The gate admitting of such distribution of metal is formed in thebody of the flask by scraping out or otherwise removing portions of theinvestment to form a space of such shape that when themolten metal ispouredinto the flask the metal molded will be thinnest at the heel ofthe plate and will gradually thicken toward the neck of the flask. Theinvestment is further scraped out or removed at the sides of the heel ofthe model in orderto admit a more ready ingress of metal and egress ofair and gases contained in the mold. Means are provided for obtaining anexcess of hydrostatic pressure and also a perfect escape for gases andair. The matrix having been formed, the investment is dried out by heat,and the metal to be poured is preferably refined as follows: A quantityof rock-salt (natural sodium chlorid) is placed in a crucible andcovered with the aluminium to be refined. Heat is then applied until allthe material in the crucible is melted, whereupon salfpeter (potassiumnitrate) is added in suitable quantity, piece by piece, the mass beingstirred and skimmed until all dross and impurities are removed. rlhemetal is now either poured into other crucibles or molds to form ingotsfor future pouring or is removed from the furnace to be cooled until itbegins to granulate. The metal is then replaced in the furnace, and whenthe grauulations again disappear (determined by stirring with a wire)the metal is at the proper heat for pouring and should be removed fromthe fire. At this time a small piece of saltpeter is added, and when itis melted the skin is broken by a wire and the metal is poured in acontinuous stream into the mold until it is full. Previous to pouringthe flask is heated, so that the neck will be the hottest portion andthe base the coolest portion to promote the proper cooling of the castmaterial. After pouring lthe flask is permitted to thoroughly cool,whereupon the cast plate is removed, all excess and gates are sawed off,and the cast plate is reduced to proper form by filing or grinding andfinished on leather buffs and rouge. \Vhen the plates are tried in themouth and are found not to fit properly, they can be swaged on the firstmodel or upon a model poured into the plate as it comes from the flaskand shaped, being properly scraped upon the exterior border to correctany defect of contraction which may occur at said point. The swaging orshaping, however, is preferably performed by the process in which themodel, with the plate on it, is placed in a cylinder, the cylinder beingfilled with shot or sand, and a plunger is driven down upon it.

It will be understood that wherever wax is employed to form the mold orto form air or gas vents the wax is melted by placing the flask (themold having been completed) in a furnace or otherwise subjecting theflask to such a degree of heat as will cause the wax employed toentirely disappear from within the flask.

The preferred form of apparatus employed for carrying out the methodabove stated is constructed as follows:

The flask A usually consists of two members 10 and l1, and the innersurface of each member of the flask is more or less inclined in orderthat the investment employed shall be firmly held in position. Themember l0 of the flask is provided With a flange 10L and the memberV 1lwith a corresponding flange 1l, the two flanges being adapted to engagewith each other and haveinterlocking connection, if desired. These wideflanges serve to render the flask tight when the members are broughttogether. Any form of locking device may be employed for locking theflask. In the drawings the locking device consists of ears 12a, formedintegrally with the flanges of the members, the ears of the membersbeing arranged to register, and bolts 12", provided wifh suitable nuts,which are passed through the said ears 12, as shown particularly inFigs. l0 and 1l. Each member of the flask is provided with a neck 14,the necks being likewise flanged and the necks of the two members whenthe flask is set up being adapted to be brought together. The neck ofeach member of the flask is provided with an inner longitudinal groove15, and when the necks of the two members are brought together thesegrooves form a gate B. The upper end of the neck, and consequently theupper end of the gate B in the neck, is made flaring, and the lowerportion 15" of the said gate B is made quite large and somewhatbell-shaped.

At each side of the gate B of the flask-neck vents 16 are formed,adapted for the outward passage of air and gas, and these vents 16 leaddirectly to the interior of the flask, as shown particularly in Figs. 5and 10. Each member of the flask is preferably provided with legs 17 atthe bottom portion of its body, so that the flask may be maintained inthe upright position during the process of pouring. The mold 18 for theplate to be cast is embedded in the investment C, which is placed, forexample, in the member lO of the flask, as shown in Figs. 2, 3, 4, and5. The mold is placed as near as possible to the bottom portion of theflask orso that the heel of' the cast plate will be as far as possiblefrom the neck of the flask. The object of the additional room at theheel of the model and also of the bell-shaped space l5" in the neck ofthe flask and the Wide mouth 15 for said neck is to admit of the properformation of pouring-gates and the admission of a body of metalsuflicient to control the shrinkage in the plate.

The investment employed may be of any desired material that will standhcatand drying. An economic material that has given IOO IIO

Wax covering or leaf of the model, extending beyond the edge of the saidcovering 19.

. second leaf or sheet 2l, of wax, is placed over the reticulatedmaterial 20, both of the wax sheets 19 and 21 and the reticulated sheet2O being made to conform to the upper side and front edge surfaces ofthemodel 18. Wax pegs 22 are secured upon the upper wax leaf 2l, and thesepegs 22 are preferably circular in cross-section, as shown in Fig. 5,although it may be given other desired shape. After the upper wax leaf21 is placed in position and pegs have been attached thereto the matingsection 11 of the flask is properly placed and secured upon the member10, and the upper member 11 of the flask is then provided with aninvestment D, corresponding to the investment in the member of ask, asshown in Fig. 4. The ask is permitted to remain untouched until theinvestment vis properly set, whereupon the investment is treated to forma gate leading from the enlargement in the main gate or gate in the neckto va point just above the face of the model on which the cast is to bemade or at the heel portion of the wax sheet 19, placed directly uponthe model. The gate vin the body ot the ask is formed upon the lines cand d, (shown broken in Fig. 6,) and a large air-vent is made in theinvestment D on the broken lines indi-v cated by the reference-letterscl in Fig. 6. The gat-ein the body of the {iask (indicated by the linesc and d) is made partially in the investments G and D. After theinvestment has been properly set and dried the members of the mold areseparated and the investment from a point at each side of the heelportion of the mold 18 to the side of the body of the mold adjacent tothe neck, is scraped or otherwise removed to form cavities, designatedas 23 and 23a and shown best in Fig. 7, which cavities are quite shallow.where they connect at the heel portion of the model or at the mold,being gradually deepened as they approach the neck until the upperportions of the cavities forming the gate in the body are combinedly aswide as the enlargement 15b at the bottom portion of the neck of theflask. That portion of the investment D located between the lines d isremoved, forming a large vent 24, which will expose a portion of the waxleaf 21 before said leaf is removed. After the gate in the body ofthediask has been made the wax is washed out with hot water and theflask is submitted to heat until it is practically red-hot, thus meltingany remaining wax contained within the flask, providing a mold-cavity25, which was formerly occupied by the wax sheet 19, and a space 26 atthe opposite side of the reticulated sheet 20, together with air and gasvents 27, which lead out through the investment D, as shown in Fig. 7.The mold is nowin a position to cast from, and it is placed upright, asshown in Figs. 6, 7, and 8, particularly Fig. 8, and the molten metal ispoured into the flask at the top of the gate B of the neck, whereuponthe metal will flow quickly downward and enter the mold-cavity 25,flooding the same with metal almost simultaneously at each and everypoint, and the heavy column of metal above the mold will serve to almostinstantly force-all the air and gases from the mold out through thevent-s 24 and 27, while the gases and air in the path of the pouredmetal above the mold will be forced out through the vents 16. Under sucha construction it will be evident that the cast will be thinnest at theheel of the plate and will gradually thicken toward the neck of theflask, as shown in Fig. 9, in which the plate 28 is shown just as it isremoved from the flask, 29 representing the thin web of metal whichconnects with the heel portion of the plate, 30 the heavy bulk of metalwhich was contained in the neck of the flask, and 3l the metal thatfound its way up into the vents 16.

In addition to scraping the investment to form the tapering gates in thebody of the flask the investment is likewise scraped away from aroundthe mold, as shown at 18a in Fig. 10, in order to permit a ready ingressof metal to the mold and the egress of air and gases contained in themold and to insure a casting that will be non-porous and perfect in itscharacter.

In Fig. 12 I have illustrated a plate 28 as having its outer sidesroughened, as shown at 32, in order that the representation of a gum maybe firmly held to the plate and wherein the teeth 34 are attached to therepresentation of the gum by means of pins 35; but I desire it to beunderstood that teeth may be formed directly upon and attached directlyto the cast plate, if desired.

Having thus described my invention, I claim as new and desire to secureby Letters Patent- 1. The herein-described method of casting aluminiumplates, which. consists in building up the members of a ask withinvestments, embedding a model in the investment of one member of theflask, covering the face of the model with a material liquefied by heat,forming air-vents in the investment of the other member of the flask,and providing in the inner face of the investment of each liask membertapering opposing cavities, which cavities form a gate, the deliveryportion of the gate extending to the heel portion of theimpression-surface of the model as set forth.

2. The herein-described method of constructing aluminium plates, whichconsists in providing a ilask with a long neck, and a gate IOO IIO

Within said neck, Whose upper and lower ends are enlarged, locatinginvestments in each member of the flask, locating a wax covering on theimpression-face of the model, providing a reticulated plate for the saidWax covering and a Wax plate for the reticulated plate, the reticulatedplate and its adjoining Wax plate being located in the investmentopposed to that in which the model is located, forming vents in theinvestment carrying the reticulated plate, the said vents bcing adaptedto communicate with plates, producing a tapering gate in the opposingfaces of the investments, Which gate communicates with the gate in theneck, the narrow end of the gate in the investment communieating withthe impression-surface of the model, and also forming vents in the neckof the flask communicating with the gate in the investments, asdescribed.

3. In adevice for casting aluminium plates, a flask constructed Withremovable members, the inner faces of' the body portion of the membersof the flask being inclined, each member being provided also with aflange where said members engage with each other, a neck formed uponeach member of the flask, each neck being provided with a longitudinalgroove,'formin g a gate adapted tov receive the metal to be poured, thesaid gate being enlarged at the top and at the bottom, each section ofthe neck being also provided at each side of the gate with opposingchannels, which extend from top to bottom of the neck, the innerportions of the channels communieating with the interior of the body ofthe flask, said channels being adapted as vents for the escape of airand gas, as specified.

4. In a device for casting aluminium plates, the combination, with aflask, provided with a neck, which neck is provided with a longitudinalgate enlarged at the top and at the bottom, and vents at each side ofthe gate, of an investment located in each section of the flask, theinner faces of the investment being channeled to form a gatecommunicating with the gate in the neck of' the flask, the gate in theinvestment being thickest at the top and thinnest at the bottom, thegate also extending at its upper portion from side to side of the flask,a model secured in the investment of one member of the flask at thepoint farthest removed from the neck, the thinner end of the gate in theinvestment leading to the impression-face of the model, the investmentin the opposite member of the flask being provided with vents leading toa point near the impression-face of the model, for the purpose setforth.

5. In a device for casting aluminium plates, the combination, with aflask provided with a neck, which neck is provided with a longitudinalgate enlarged at the top and at the bottom, and vents at each side ofthe gate, of an investment located in each section of the flask, theinner faces of the investment being channeled to form a gatecommunicating with the gate in the neck of the flask, the gate in theinvestment being thickest at the top and thinnest at the bottom, thegate also extending at its upper portion from side to side of the flask,a model secured in the investment of one member of the flask at a pointfarthest removed from the neck, the thinnest end of the gate in theinvestment leading to the impression-face of the model, the investmentin the opposite member of the flask being provided with a reticulatedplate which is spaced from and extends over the impression-surface ofthe model, the investment to which the reticulated plate is attachedbeing provided With vents leading to said reticulated plate,substantially as set forth.

VILLARD STREETMAN.

lVitnesses:

W. J. STEWART, N. E. I-IIGHTOWER.

